Plunger actuated switch



1967 E. E. KUSSMAUL 3,354,731

PLUNGER ACTUATED SWITCH Filed Feb. 25, 1966 INVENTOR. EDWIN E. K SSMAUL my? I i ATTORNEYS r 3,354,731 United States Patent cc 1 2 abuts the shell and the plunger reaches its outer ex- 3,354,731 PLUNGER ACTUATED SWITCH Edwin E. Kussmaul, Westwood, Mass., assignor to Kelek Company, N orwood, Mass, a corporation of Massachusetts Filed Feb. 25, 1966, Ser. No. 529,991 5 Claims. (Cl. 74-55) The present invention relates generally to switch mechanisms, and more particularly to a switch adapted for actuation at an adjustable position in the travel of a plunger such as a cam-reciprocated plunger.

A principal object of this invention is to provide a rugged mechanism that can be accurately and conveniently adjusted to set both the limit positions between which the operative parts are moved and the position of the controlling means in which it causes actuation of the switch, such adjustment to be made by tools engaging only externally exposed parts.

In many switch mechanisms of this general type adjustments cannot be made unless the units are at least partially disassembled as by removing covers, which is not only time consuming but may result in damage to delicate switch parts enclosed within the assembly. Such partial disassembly may also lead to contamination by dirt, grease or other foreign matter present in the machine or apparatus where the switch is employed.

Often, for example, so-called microswitches are used in these assemblies, such switches having relatively delicate internal parts. The common practice is to have the plunger reciprocated along an axis'normal tothat of the operator element of the switch, depressing the latter by a sliding cam action, thus preventing the transmission of excessive external forces through the plunger to the switch parts and also preventing overtravel of the operator. After such a switch is mounted in a machine opposite the element thereof which actuates the plunger it is often difii cult to reach the switch with tools for final assembly adjustment, not only because of inaccessibility of the location within the machine but also because of the direction or directions from which the tools must be applied as well as the clearances that are needed to accommodate the movement of the tools. It is accordingly another object of this invention to provide external adjusting means that may be manipulated with precision by the use of common tools such as screwdrivers and pliers or wrenches to provide accurate adjustments without any substantial risk of damage to delicate internal parts.

A related object is to provide exposed and easily accessible means for adjustment permitting switches to be gauged while yet allowing individual adjustments of each switch, as required for example in a ganged switch assem bly arranged along a timing cam shaft containing a number of cams.

With the foregoing and other objects in view, as will hereinafter appear, the features of this invention reside in a novel construction of a plunger actuated switch mechanism including a threaded screw, a plunger and a block, these parts being threaded together and slidably supported within a shell and also being adjustable by externally applied tools to control both the outer limit of the plunger and the depressed position thereof in which the internally-housed switch is to be operated.

The plunger effectively extends the length of the screw, provides a surface for sliding within the shell, and provides a bearing end engageable with external means of actuation such as a cam or any other means adapted to depress a plunger. The block is restrained from rotation wtihin the shell, whereby it is caused to slide longitudinally of the screw when the screw is turned. Spring means tend to bias the screw to a position in which its head tremity. 4

Other features of the invention reside in certain details of the assembly and in the relationships of the parts that will become evident from the following description of a preferred embodiment illustrated in the appended drawing, in which FIG. 1 is a side elevation, partly in section, of the switch mechanism with the cover removed; and

FIG. 2 is a detail view showing an alternative form of the plunger.

Referring to the drawings, I provide a shell 12 for the switch mechanism of one piece or built-up construction, preferably of insulating material, which defines an enclosure space 14 in which a switch 16 is conveniently housed and mounted by suitable means such as screws 18. A projecting operator element 20 on the switch is to be depressed when a rotating cam 22 in the machine or apparatus reaches a selected angular position, the element being depressed by a block 24 threaded on a screw 26 and freely slidable upon an inner surface of the shell 12. The shell, the body of the switch and the block are preferably of rectangular cross section and so dimensioned that the block is prevented from rotation about the axis screw 26. A plunger 28 is adjustably threaded upon the screw and slidably extends from the shell int-o a position for engagement with the cam 22. The cam rotates continuously or intermittently, depending on the particular characteristics of the machine or apparatus on which the switch is employed, and engages and depresses the plunger 28, causing the block 24 to move toward the operator 20 until it engages the operator and actuates the switch. The plunger may continue thereafter to move in the same direction, and if desired it may move entirely to the other side of the switch, allowing the operator to return to its upper position if it is internally biased so to do, until the cam allows the plunger to return to its outer limit.

The shell may be of simple rectangular form comprising a five-sided rectangular box of built-up phenolic sheets, or integrally molded in one piece with a removable cover provided for the open side. As will be evident from the following discussion the cover is not removed to perform the necessary assembly adjustments.

The switch 16 may be any type of switch such as a socalled microswitch, and may comprise either a single switch or a gang of switches the connections to which are brought out of the shell in any desired manner through suitable holes. The operator 20 of the switch is normally biased outwardly, as is commonly known. The plunger 28 and the block 24 are preferably fabricated of plastic insulating material, although this is often unnecessary where the operator element 20 is itself made of an insulating material. I prefer to fabricate the plunger 28 and the block 24 of nylon. The plunger 28 has a portion 28a of larger diameter slidable within a bearing 30 in the shell and a portion 28b of reduced diameter shaped to receive an adjusting tool such as pliers or a wrench. I also provide a nylon bearing 32 fitted in another opening of the shell, this latter bearing slidably receiving the shank of the screw 26. An inner clearance between the bearing 32 and the screw 26 receives one end of a compression spring 34 bearing at,the other end upon the block 24. When the plunger 28 is out of contact with the cam 22 the spring 34 urges the block 24, the plunger 28 and the screw 26 in the direction of the cam until they are arrested by the head 26a of the screw abutting the shell.

There are two kinds of adjustment that may be carried out by application of turning tools to the head 26a of the screw and the reduced portion 28b of the plunger. The head of the screw is shown as slotted to accommodate a screwdriver, for example, while the plunger may be turned by grasping it with a pair of pliers, although it is. obvious that these are. only examples of suitable tools.

The first adjustment consists in setting the outer limit of the plunger 28 in relation to its actuating means such as the cam 22 by turning the screw while restraining the plunger from rotation with the screw head abutting the. shell as illustrated. This determines the position of the cam in which engagement and depression of the plunge! are initiated. It likewise determines the total outward movement of the screw since the latter equals the throw of the cam between the position of engagement and the position of maximum throw of the cam.

The second adjustment is thereafter obtained with the cam engaging the plunger in the position of the cam at which the switch 16 is desired to be actuated. In this adjustment the screw is rotated without restraining the plunger from rotation. The screw 26. is turned until the block 24 reaches and actuates the operator element of the switch.

The block 24 has a cam surface 24a for sliding engagement with. the operator 20. If desired, a second cam surface may be provided on the block for depression of the operator if the stroke of the plunger is sufficient to move the block entirely past the operator.

FIG. 2 shows a variant of the plunger designated 28'. This variant provides. a superior device for actuation by a cam, comprising a metal ball bearing 36 received within a socket in the end of the plunger. Conveniently, the plunger is made of nylon into which a blind hole is bored longitudinally of its axis, the diameter and depth of the hole both being approximately three quarters of the diameter of the ball. The sides of the hole are then reamed out suit-ably to accommodate the ball resiliently in the position shown.

It will be understood that while the invention has been shown in a preferred. embodiment, numerous variations are possible, andthese may be accommodated consistently with retention of the adjustment features hitherto discussed. Suchvariations areintended to be within the spirit and scope of this invention.

Having thus described the invention, I claim:

1. A plunger actuated switch mechanism having, in. combination,

a shell defining an enclosure and having a pair of aligned openings defining bearings in the wall thereof,

a switch mounted in said. enclosure and having a projecting operator element displaceable normally to the bearings,

a threaded screw slid'able in one of said bearings and having a head exterior to and engageable with the shell,

a plunger slidable in and extending from the other of said bearings and threaded upon the. screw,

a block threaded upon the screw between the head and the plunger and adapted upon sliding of the screw and plunger to engage the operator element,

and a spring urging the block toward; said other bearing and thereby urging the head" toward engagement with the shell.

2. The combination according to claim 1, in which the spring is a compression spring bearing at one end upon the shell.

3. The combination according to claim 1, in which the parts are adapted to prevent rotation of the block when the screw is rotated.

4. The combination according to claim 3, in: whichthey screw and plunger are adapted to receive turningtools.

5. The combination according to claim 1, in which the plunger has an end adapted for sliding engagement with a cam surface.

References Cited UNITED STATES PATENTS 1,913,617 6/1933 Smith 200-4 66 2,650,275 8/1953 Doutt 200-4'7- 3,110,425 11/ 1963 Fuller 74--55 FOREIGN PATENTS 300,990 8/ 1929 Great Britain. 602,967 6/ 1948 Great Britain.

FRED C. MATTERN, JR., Primary Examiner.

W. S. RATLIFF, Assistant Examiner. 

1. A PLUNGER ACTUATED SWITCH MECHANISM HAVING, IN COMBINATION, A SHELL DEFINING AN ENCLOSURE AND HAVING A PAIR OF ALIGNED OPENINGS DEFINING BEARINGS IN THE WALL THEREOF, A SWITCH MOUNTED IN SAID ENCLOSURE AND HAVING A PROJECTING OPERATOR ELEMENT DISPLACEABLE NORMALLY TO THE BEARINGS, A THREADED SCREW SLIDABLE IN ONE OF SAID BEARINGS AND HAVING A HEAD EXTERIOR TO AN ENGAGEABLE WITH THE SHELL, A PLUNGER SLIDABLE IN AND EXTENDING FROM THE OTHER OF SAID BEARINGS AND THREADED UPON THE SCREW, A BLOCK THREADED UPON THE SCREW BETWEEN THE HEAD AND THE PLUNGER AND ADAPTED UPON SLIDING OF THE SCREW AND PLUNGER TO ENGAGE THE OPERATOR ELEMENT, AND A SPRING URGING THE BLOCK TOWARD SAID OTHER BEARING AND THEREBY URGING THE HEAD TOWARD ENGAGEMENT WITH THE SHELL. 